Adaptable voltage control for a variable gain amplifier

Abstract

A method and apparatus for adaptively controlling a variable gain amplifier (VGA). The operation of the VGA is separated into a low gain mode and a high gain mode and the mode in which the VGA is currently operating in is adaptively sensed. A threshold voltage is compared to a control voltage of the VGA; if the VGA is currently operating in the low gain mode and the control voltage is higher than the threshold voltage, the VGA is switched from the low gain mode to the high gain mode; and if the VGA is currently operating in the high gain mode and the control voltage is lower than the threshold voltage, the VGA is switched from the high gain mode to the low gain mode.

Description

FIELD OF THE INVENTION [0001] This application is related to variable gain amplifier (VGA) circuits, and more particularly to an adaptable voltage control for a two-band VGA. BACKGROUND OF THE INVENTION [0002] In high speed (e.g., 10 giga bits per second (Gb / s)), high performance, serial communication receivers that require equalization, variable gain amplifiers (VGAs) are sometimes used on the front end of the topology. The VGA is used to either provide gain or attenuation depending on the amplitude of the input signal such that the VGA outputs a substantially constant amplitude signal. The ability to adjust the gain / attenuation of the VGA so that both a very large and very small input voltage swing range at the input to the receiver can be accommodated is desirable for 10 Gb / s serial data communication applications. [0003] Depending on the application, there may be system requirements in which the minimum and maximum input swing range at the input to the receiver is very wide. Thu...

AI Technical Summary

Benefits of technology

[0005] In one embodiment, the present invention is directed to a method and circuit for adaptively controlling a VGA. The operation of the VGA is separated into a low gain mode and a high gain mode and the mode in which the VGA is currently operating in is adaptively sensed. A threshold voltage is compared to a control voltage of the VGA; if the VGA is currently operating in the low gain mode and the control voltage is higher than the threshold voltage, the VGA is switched from the low gain mode to the high gain mode; and if the VGA is currently operating in the high gain mode and the control voltage is lower than the threshold voltage, the VGA is switched from the high gain mode to the low gain mode.

[0006] In another embodiment, the p

Problems solved by technology

Thus, it can be difficult to design a VGA block capable of covering this wide input dynamic range while still being robust to manufacturing process, power supply (VDD), and temperature variations (hereby designated as PVT).

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